1. Field of the Invention
The present invention relates to an image processing apparatus, and an image processing method, computer program and storage medium, which can treat paper fingerprint information.
2. Description of the Related Art
Recently, with the wide spread use of multi-functional image processing apparatuses capable of copying, the importance of security therewith has been increasingly noticed. The multi-functional image processing apparatus, while being convenient, might invite leaks of confidential information or illegal document falsification depending on its usage. Accordingly, multi-functional copying machines are provided with an anti-counterfeiting device or a copy guard function. Also, techniques for discriminating characteristics of paper itself and ensuring uniqueness or originality of a document based on the paper discrimination have been developed (refer to Japanese Patent Laid-Open No. 2004-102562).
When the technique disclosed in Japanese Patent Laid-Open No. 2004-102562 is used, however, there is a problem that a fabric pattern specific to paper (paper fingerprint) can not be discriminated without a special reading apparatus. To solve this problem, reading devices of widely used multi-function copying machines might be utilized for reading out the paper fingerprint. However, for reading out the paper fingerprint specific to paper properly, it is necessary to do so by reducing light intensity (or gain) to a level where a background color of the paper can be read out. At this time, if a copying process is done at the same time with the paper fingerprint extraction in this condition, an image to be copied will be output overlapped with the background color. This is caused because the background color of the paper is reproduced by the copying process in the reduced read-out level.
For solving this problem, there may be devised a method in which the reading is performed twice by changing light intensity (or gain). That is, for acquiring the paper fingerprint, it is necessary to carry out another scanning by changing light intensity (or gain) separately from a reading operation (scanning) for the copying.
A technique utilizing a paper fingerprint is an important technique for ensuring originality of a document, but there still remain problems to be overcome for acquiring the paper fingerprint efficiently. For example, conventionally, it is necessary to carry out scanning twice for acquiring the paper fingerprint as described above and it is desired to improve productivity of the scanning.
Also, there is a desire to acquire the useful paper fingerprint as described above, even in a scanner with a configuration in which the same document can not be read twice, as in the case where it is skimmed.